In a closed-door Republican caucus before the marathon floor session, DeVore made a motion to remove Villines as GOP leader (known as "vacating the chair" in Capitol-speak). None of the other 28 Republican Assembly members seconded the motion.

"The discussion was a credit to the caucus. Nobody raised their voice, everything was logical, people made their case and I lost," said DeVore, who is plotting a 2010 run for U.S. Senate.

DeVore's motion was not seconded despite the fact that 25 of his all of his Assembly GOP colleagues have endorsed him* in his bid to unseat Sen. Barbara Boxer, including Villines himself.

*UPDATE: DeVore wrote in to say that every Republican Assembly member has endorsed his U.S. Senate campaign.

The leadership challenge came a day after a supposedly private e-mail from DeVore to Villines was publicized on the John and Ken radio show in Los Angeles.

In the e-mail, DeVore wrote that "for the caucus, for the party and for the upcoming elections, if this is the final (budget) deal and you believe it to be good...then I think you need to resign or be replaced the day of the vote," according to the radio show.

DeVore confirmed the authenticity of the e-mail, though he denied that he leaked it to the conservative radio shock jocks. Only a day earlier, John and Ken had blasted DeVore on air for not challenging Villines' leadership more directly.

How then would a private e-mail between the two become public?

DeVore said he had forwarded the e-mail to "some of my members, colleagues" -- at their request -- "because it contained kind of a logical rundown of why I thought what we were about to do was in error."

"Clearly, I should not have sent that to anyone else other than Mike Villines, because obviously the last paragraph was kind of a bombshell," he said, suggesting someone else forwarded the e-mail to the radio hosts.

In the end, instead of Villines resigning, DeVore did.

He announced on Saturday night that he would give up his post as a GOP whip. DeVore had been one of 14 members of the 29-person caucus to technically serve in Villines' leadership team.

DeVore said he couldn't remain a part of the team "in good conscience." He said he feared voting for tax hikes to solve California's massive $40 billion budget deficit would "be very harmful to the cause of limited government."

"I think it is going to discourage our base," he said. "I think that no good thing will come from it."

In the Senate, Republican leader Dave Cogdill of Modesto could face challenges of his own. As the chief Senate Republican negotiator, he had a hand in crafting the budget package that has yet to garner the necessary support of three members of his caucus.

Shortly before dawn Sunday, in the midst of the all-night marathon session, Cogdill offered to give up his post in a closed-door meeting of GOP senators. The caucus did not accept his offer -- for now.

"Nobody wants to use the challenges of the moment to make any kind of an issue or a decision," said Sen. George Runner, R-Antelope Valley, who noted that Cogdill had made "great personal sacrifice" in the budget negotiations.

"I think right now everybody's focused on the discussion with the budget," said Runner. As for Cogdill's position as leader "whatever comes of that will come of that...I'm not even going to guess what's that's going to be."